1. Field of the Invention
This invention relates to a structural assembly including a bar joist or metal roof truss. More specifically, this invention relates to a bar joist having an expanded metal lath secured against it and a layer of cementitious material enclosing the structural elements of the bar joist and adhering to the lath to permit the joist to withstand fire temperatures without losing its strength. The invention also relates in such an environment to a clip for holding the lath against the joist members during the depositing of the cementitious layer.
2. Description of Related Art including Information Disclosed under .sctn..sctn.1.97 to 1.99
Fireproofing of metal structures such as bar joists has been accomplished by depositing on the structural elements--the bars and flanges--an insulating material as described, for instance, in U.S. Pat. No. 4,584,811 to Balinski which issued Apr. 29, 1986. Fireproofing of bar joists in roof structures is necessary to prevent the loss of strength from overheating in a hot fire.
In the fireproofing process cementitious material is sprayed over the bar joist elements to a thickness of 2" or so to insulate them from the heat. The problem inherent in such a treatment process is that the bar joist, which comprises a number of zig-zag arranged bars running back and forth between upper and lower angles, is so open that it is difficult to make the material adhere to the elements. To solve this problem, fabricators and suppliers of material in the past have secured an expanded metal lath against the bar joist elements. This has usually been done by wiring the lath to the elements.
The wiring described above has been time and energy consuming. It has involved poking a wire through the lath, around the structural element, back through the lath and twisting the ends of the wire together. With such an assembly, the cementitious material is "caught" by the lath and held in position against the structural elements: little sprayed material passes through the lath to fall wastefully on the floor.